Micropropagation of 4-year-old elite Eucalyptus tereticornis trees

A protocol for the micropropagation of mature Eucalyptus tereticornis Smith has been developed using regenerated shoots from axillary bud explants. The trees were selected on the basis of their better growth rate, physical and phenotypic characteristics and freedom from disease. Regeneration was obtained in modified Murashige and Skoog (1962) medium. Evaluation of explant regeneration throughout the year indicated that the incidence of browning of explants was maximum during the month of February, while dominance of the microbes in endogenously infected explants peaked in August-September. Regeneration from primary explants was maximum during the months of March-April. Subcultures were carried out every 4 weeks. Effects of hormones and media composition on regeneration and growth were studied. Phytagel induced vitrification, while calcium chloride dihydrate reduced vitrification and induced the elongation of shoots. Best rooting was obtained with half-strength, modified MS medium supplemented with 1.0 mg/l indolebutyric acid. Plantlets were hardened in a nonsterile potting mix at high humidity and gradually exposed to the ambient environment over a period of 6 weeks, and upon transfer to field conditions the survival rate varied from 84% to 100%.